1.3. CAPTCHA Settings

You can configure OJS to use CAPTCHA challenges to prevent user registration and comment abuse. Find the
CAPTCHA Settings section in config.inc.php and uncomment and change
to the following:

[captcha]
; Whether or not to enable Captcha features
captcha = On
; Whether or not to use Captcha on user registration
captcha_on_register = On
; Whether or not to use Captcha on user comments
captcha_on_comments = On
; Font location for font to use in Captcha images
font_location = /usr/share/fonts/truetype/freefont/FreeSerif.ttf

Please note that your server needs to support the GD (PHP4) or GD2 (PHP5) library for this to work,
and that you need to point your font_location variable to a font that
exists on your system, which may be different than the default provided.